The Apple Double Format, Network Shares and uTorrent

This might be a bit of an edge case for most people but for those of us with heterogeneous networks with a mixture of Windows and Mac OS X computers you may come across hidden files starting with “._” (so something like “._humptydumpty.doc”) and may or may not correspond with a filename of the same name with out the leading “._”.

So what is it?

Basically, it’s a leftover from older versions of Mac OS prior to Mac OS X that used “resource forks” to store file information. There would be a “data fork” that contained the actually file information and a “resource fork” containing descriptive information about the file.

For me, this is particularly problematic when trying to have torrents load automatically from a folder on the Windows Home Server box as the resource forks with filenames starting with “._” and ending in “.torrent” take alphabetical precedence over the actual torrent files themselves. The problem this creates is that uTorrent will get stuck on the resource forks and not load the proper torrent files.

So how can we fix this?

The best solution I have found for my situation is to force the Mac OS X machines in the household to enable the use of “streams” on network shares that support them (such as NTFS formatted drives like the three in the Windows Home Server box). The “Alternate Data Streams” or ADS feature in NTFS provides a seamless way to store the same information.

To enable the use of streams open a terminal window on the Mac OS X machines and type in the following:

  • echo “[default]” | sudo tee -a /etc/nsmb.conf
  • echo “streams=yes” | sudo tee -a /etc/nsmb.conf

What this does is enable the use of named data streams for all user accounts on the computer when using SMB (Server Message Block or “Samba”) network shares.

I am in the process of testing how this works on Windows Home Server 2011 with Drive Bender installed (hopefully I don’t hose anything but it’s in the spirit of testing). The original Windows Home Server did suffer from a major data corruption bug with files and data streams but this was corrected in the first major update to the operating system (Power Pack 1). I’ll report back either way and let you know the results.


    • Mark on August 2, 2011 at 16:09
    • Reply

    Hey Chan-Man

    Do you know if this is for Snow Leopard and/or Lion?


    1. This was definitely for Snow Leopard and earlier. I heard rumours about Lion using a different SMB module but have yet to try changing the configuration on the new MacBook Air (as well as setting up Time Machine).

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